An Overview about the Chemical Element Terbium


Symbol: Tb

Atomic Number: 65

Atomic Mass: 158.92534 amu (atomic mass units)

Melting Point: 1360.0°C (1633.15 K, 2480.0°F)

Boiling Point: 3041.0°C (3314.15 K, 5505.°F)

Number of Protons: 65

Number of Electrons: 65

Number of Neutrons: 94

Classification: Rare Earth

Crystal Structure: Hexagonal

Density @ 293 K: 8.27 grams per cubic centimeter

Color: silver-gray

Terbium was first discovered in the mineral ore gadolinite. This ore was found in a quarry near the town of Ytterby in Sweden. In 1843 the Swedish scientist Carl Gustaf Mosander split a sample of gadolinite into three separate materials which he named after the town .These names were yttria, erbia and terbia. Owing to the similarities scientists soon reversed these and erbia became terbia while terbia became erbia. Mosander went on to discover the elements erbium and terbium from these substances. There are now four elements named after the town of Ytterby they are erbium, terbium, yttrium and ytterbium. Of these four elements all but yttrium are rare earth elements.

The element is a rare earth metal belonging to the lanthanide or lanthanoid series. Terbium is fairly stable in air. This soft, malleable and ductile metal can be cut with a knife.

There is only one naturally occurring isotope of the element that is terbia-159 and it is stable. Over fifty unstable isotopes of Terbium have been recognized with half lives ranging from 15 milliseconds to 180 years.

Terbium can be extracted from the minerals euxenite and xenotime but it is most commonly extracted from monazite sands which is rich in many rare earth elements. Some deposits of monazite can contain as much as 0.03% terbium. The metal is purified from the lanthanide salt mixtures prepared from these ores by the solvent extraction and ion exchange processes. Care must be taken when extracting the rare earth element from monazite as it also contains the highly radioactive element thorium. Once purified terbium and its compounds has been found to have a few industrial uses,

* Terbium is used to dope calcium fluoride, calcium tungstate and strontium molybdate for use in some solid state devices.

* It is used, along with the element zirconium, as a crystal stabilizer in fuel cells which are designed to run at high temperatures.

* Terbium oxide has the potential to be used as a green phosphor activator in color television sets.

* Terbium borate is used in laser technology.